THE KANSAS CITY BRIDGE. 117

It will be noted from the above, that the cost of the bridge proper was
$886,171.78, or $637.08 per lineal foot. While this does not materially differ
in the aggregate from the cost of similar structures over the Mississippi River,
yet the cost per running foot is nearly twice as great, in consequence of the
deep and difficult nature of the foundations, and the greatly increased height
of the piers.

If, however, the cost be referred, as is sometimes done, tothe area enclosed
between the top of the bridge superstructure, and the bottom of its foundations,
it will be found, that as this cross section measures 147,020 square feet, the
cost has been $6.03 per square foot of the areaso enclosed, which will compare
favorably with similar works.

It must be remembered that all the foundations have been put in for a
double-track bridge, up to low water, so that in the not improbable event that
the traffic shall require it, the capacity of the bridge can be doubled at no very
great cost.

No separate account was kept of the additional cost occasioned by the
accommodation of the roadway to the wagon traffic, but it may be stated in
round numbers at about $40,000.

It is not expected that any further expenditures will be required for the
next ten or fifteen years, save for the maintenance of the river protection, upon
which depends the permanence of the river bank and channel, as well as the
harbor at Kansas City, and for the renewal of the upper works of the draw pro-
tection, which are of wood.

The wood and iron combination of the fixed spans being experimental, so
far as duration is concerned, there are no data at hand upon which to pre-
dicate an estimate of their life. It may be stated, however, that a superstructure
all of iron would have cost $72,000 more, and that as all the wooden parts can be
replaced for $23,000, it follows that the compound interest alone at 7 per cent.
upon the sum saved, will renew all the perishable portions of the superstructure
with wood every four years, while at the end of fifteen years it would be suffi-
cient to renew them all with iron.

It is believed that the combination adopted, and the pains which have been
tuken for its preservation, may insure for it even a longer life than this.